TECHNICAL REPORTS Intelligent Positioning Modules for Programmable Logic Controllers by Shun Ohta and Haruhiko Kondo* Factory automation systems are being used to manage more varied and complicated tasks. Intelligent modules are a key to implementing these systems because they extend and comple- ment the functions of programmable logic con- trollers (PLCs). Intelligent modules offer such functions as analog-to-digital (AD) and digital- to-analog (DA) conversion, high-speed count- ing, temperature input and positioning control. This article introduces the AD75 Series posi- tioning modules. Description The AD75 Series offers dramatic enhancements over the previous AD71 Series in performance, functionality and versatility. Use of a 32b RISC processor with peripheral circuits implemented in custom LSIs gives the series high perfor- mance and compact dimensions. A program- ming software package for the series supports creation of positioning data, monitoring of module operating status, and other program- ming and maintenance tasks. a) A1SD75P3 b) AD75P3 Lineup The AD 75 Series offers 1- to 3-axis control Fig. 1 The positioning modules. modules for MELSEC A, QnA and A1S series PLCs. All modules consume only a single slot, which contributes to reduced equipment size ment. and cost. Fig. 1 shows the A1SD75P3 and Six functions for origin recovery when acti- AD75P3 three-axis positioning modules. vated support a wide variety of applications. Step and S-curve acceleration patterns may Functions and Performance be selected to minimize impacts associated with Three-axis independent control, two-axis lin- axis start and stop operations. ear interpolation, two-axis circular interpola- Open collector and differential pulse train tion and continuous positioning control motor drive interfaces support a wide variety of functions are supported. These functions can motor drives. The differential interface can be combined for continuous positioning con- output pulses at rates up to 400kHz to support trol and are thus capable of supporting up to high-speed motor control. Table 1 summarizes 600 points, which supports extremely compli- the AD75 Series functions and performance. cated control functions. External signal inputs for startup and speed- Programming position switching reduce scanning demands Positioning statements use the table position- on the sequencing program and the associated ing scheme of the AD71 Series for backward response delays. The PLC processing time re- compatibility and easy upgrading. quired for positioning control is reduced by 75% The AD75 Series has internal parameters con- compared to previous positioning units, which trolling movement conditions and simulta- leads to shorter tact times for controlled equip- neous start conditions for other-axis start, *Shun Ohta and Haruhiko Kondo are with the Nagoya Works. September 1996 · 7 TECHNICAL REPORTS Table 1 Specifications of the AD75 Series Positioning Modules Parameters\Products AD75P1, A1SD75P1 AD75P2, A1SD75P2 AD75P3, A1SD75P3 I/O points 32 2-axis simultaneous, 3-axis simultaneous, Control capability 1 axis 2-axis independent 3-axis independent Pulse output Open collector, differential driver Control method Point-to-point control, continuous control (linear or circular), speed control, speed-position control Interpolation None 2-axis liner/circular interpolation Positioning Language Table method Position pattern 600 patterns per axis Memory Battery-less flash EEPROM program storage −214,748,364.8 ~ 214,748,364.7μm, −21,474.83648 ~ 21,474.83647 inches, 0 ~ 359.99999 degrees, Absolute position limits −2,147,483,648 ~ 2,147,483,647 pulses −214,748,364.8 ~ 214,748,364.7μm, −21,474.83648 ~ 21,474.83647 inches, Increment limits −21,474.83648 ~ 21,474.83647 degrees, −2,147,483,648 ~ 2,147,483,647 pulses Speed instruction range 0.01~ 6,000,000.00mm/min, 0.001~ 600,000in./min, 0.001~ 600,000°/min, 1~ 1,000,000 pulses/s Acceleration processing Automatic step acceleration, automatic S-curve acceleration Acceleration time 1.0 ~ 65,535ms, four patterns each for acceleration and deceleration Startup time Less than 20ms Compensation Electronic gear 0 ~ 65,535 × position instruction unit Backlash compensation 0 ~ 65,535 × position instruction unit Error compensation function Compensates for systematic mechanical errors (includes electronic gear support) Origin recovery functions Near-point dog, count (2), stopper (3), external signal (2) Manual operation Supports one manually operated rotary encoder for each axis Error and I/O display Provided by 2.5 digit LED display which reduces sequence programming require- Positioning Module Software Package ments and provides high-precision positioning This software package, which operates under that is not dependent on sequence program scan the Mitsubishi Electric A7PHP/A7HGP periph- time. Parameter setting is performed using an eral unit or a personal computer, offers edit, optional positioning module software package. monitor and test modes, with simple switch- Positioning data is stored in flash memory, ing from editing to online monitoring or test- eliminating battery-related maintenance re- ing. Fig. 2 shows the top-level edit-mode screen, quirements. and Fig. 3 the screen for positioning data edit- ing. Positioning data editing is assisted by aux- Monitor Functions iliary windows for displaying menus and setting The module has a 2.5 digit LED display that ranges. can be used to monitor zero-point signal inputs The test and monitor modes permit detailed and mechanical inputs such as near-point dog monitoring of the module’s current status and and upper/lower limits for quicker equipment operation history. The user can select monitor- installation and adjustment. The display also ing of current feed position and feed speed for outputs error codes to facilitate troubleshoot- each axis as well as error history, warning his- ing. tory, external I/O signals and the state of the 8 · Mitsubishi Electric ADVANCE